Measurement of Bubbly Two-Phase Flow in a Vertical Pipe Using Ultrasonic Velocity Profiler and Digital Optical Imaging

Abstract

In this study, a novel measurement framework for two-phase air-water bubbly flow has been developed. It consists of ultrasonic and digital optical imaging systems. The measured parameters include instantaneous velocity profiles of the two phases, void fraction and bubble size of the gas phase. The simultaneous velocity profiles of both phases are measured by the state-of-the-art multiwave Ultrasonic Velocity Profile method - multiwave UVP for short. The void fraction and bubble size are measured by a digital imaging system that exploits high-speed video imaging. Non-intrusive measurement of these instantaneous flow parameters is still a challenge in two-phase flow study. In the present investigation, two ultrasonic signal processing algorithms have been implemented and tested, namely Doppler signal processing and correlation one. Similarly, rigorous digital image processing algorithms implemented in ImageJ tool have been exploited and tested to obtain the average void fraction and bubble size distribution. Furthermore, measurements and analyses have been carried out for various flow conditions. For the particular flow configuration investigated, important experimental data of the two-phase counter-current bubbly flow have been successfully obtained for the first time. The measured data are useful for both experimental and numerical analyses, especially computational fluid dynamics - CFD analyses, of two-phase flows.